Background: Tongue metastasis of renal cell carcinoma (RCC) is rare. Treatment is hindered by the proximity of anatomic structures involved in swallowing, speech and mastication. It is, moreover, radioresistant.

Methods: We report a case of inaugural isolated tongue metastasis, where biopsy redirected diagnosis to RCC. To avoid potentially mutilating excision in a metastatic disease of poor prognosis, treatment was local, consisting in interstitial brachytherapy, enabling a high dose (65Gy) to be delivered. Despite initially complete response, recurrence at 10.5months required salvage surgery.

Conclusions: Brachytherapy allowed a higher dose to be delivered than with external beam radiation therapy, previously reported for similar cases. This dose, which can usually be expected to ensure local control in 90% of squamous cell carcinomas of the tongue, obtained 10months' response, insufficient to avoid salvage surgery.